import java.util.LinkedList;
import java.util.Queue;

class MyStackUsQueue {
    public Queue<Integer>queue1;
    public Queue<Integer>queue2;

    public MyStackUsQueue(){
        queue1=new LinkedList<>();
        queue2=new LinkedList<>();

    }
    public void push(int x){
        if (empty()){
            queue1.offer(x);
        }
        if (!queue1.isEmpty()){
            queue1.offer(x);
        }
        if (!queue2.isEmpty()){
            queue2.offer(x);
        }

    }
    public int pop(){
        if (empty()){
            return -1;
        }
        if (!queue1.isEmpty()){
            int size=queue1.size();
            for (int i = 0; i <size-1 ; i++) {

                queue2.offer(queue1.poll());

            }
            return queue1.poll();
        }else {
            int size=queue2.size();
            for (int i = 0; i <size-1 ; i++) {
                queue1.offer(queue2.poll());
            }
            return queue2.poll();

        }

    }
    public int top(){
        if (empty()){
            return -1;
        }
        if (!queue1.isEmpty()){
            int size=queue1.size();
            int ret=-1;
            for (int i = 0; i <size; i++) {
                ret=queue1.poll();
                queue2.offer(ret);
            }
            return ret;
        }else {
            int size=queue2.size();
            int ret=-1;
            for (int i = 0; i <size; i++) {
                ret=queue2.poll();
                queue1.offer(ret);
            }
            return ret;
        }
    }
    public boolean empty(){
        return queue1.isEmpty()&&queue2.isEmpty();
    }

}
